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    <meta charset="UTF-8">
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    <title>Document</title>
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<body>
    <script>
        //  typeof 运算符   返回值一定是一个字符串
        // 能够检测出六中返回值类型   1  "number"  2  "string"  3  "object"  4 "undefined"      5 "boolean"        6 function 
        // 123       "123"        null     undefined        true/false     

        // var a;\

        // var a = {
        //     name: "张三",
        //     age: 18,
        //     sayName: function () {
        //         console.log(this.age)
        //     }
        // }

        /*

        
        /*


        */


        // */
        console.log(a)
        a = 123
    </script>
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